Comment 2 for bug 1885304

Please note that although the Python traceback I posted cited a user-installed (via pip) version of python-xlib, the same symptom does also occur with the Ubuntu-packaged version in /usr/lib/python2.7/dist-packages/Xlib/.

It is possible that the actual bug is GDM failing to correctly populate the display number in the $XAUTHORITY file /run/user/$UID/gdm/Xauthority; this bug report presumes (without justification) that an empty display number in the Xauthority file has a valid interpretation, but that python-xlib is not applying it. I note that other X applications (e.g., xclock) still work with "si:localuser:$USER" removed from the xhost list; I have only observed the failing behaviour with python-xlib and python3-xlib.